1. Technical Field
The present invention relates to an electro-optical device and an electronic apparatus having a substrate in which a plurality of step portions are formed in a lower layer and contact hole are formed in a plurality of upper layers so as to electrically connect the plurality of upper layers.
2. Related Art
In general, an electro-optical device, for example, a liquid crystal device includes two substrates formed of, for example, glass or quartz that are opposite to each other and a liquid crystal layer interposed between the two substrates. On one of the substrates, a plurality of pixel electrodes and a plurality of switching elements, for example, thin film transistors (hereinafter, referred to as TFTs) are disposed in a matrix, and a counter electrode is formed on the other substrate. Image display is performed by changing the optical characteristics of the liquid crystal layer interposed between the two substrates according to image signals.
That is, image signals are supplied to the plurality of pixel electrodes (ITO; indium tin oxide) disposed In a matrix through the switching elements such as TFTs. A voltage is applied to the liquid crystal layer between the pixel electrodes and the counter electrode on the basis of the image signals, thereby changing the alignment of the liquid crystal molecules. The change in the alignment of the liquid crystal molecules causes a change in the transmittance of each pixel, thereby changing the transmittance of light passing through the pixel electrodes and the liquid crystal layer on the basis of the image signals. In this way, image display is performed.
The TFTs are turned on by supplying scanning signals to gate electrodes through scanning lines. Then, the image signals supplied to source regions of semiconductor films through data lines are supplied to the pixel electrodes through the TFTs in the on state, thereby performing image display.
The source regions of the semiconductor films and the data lines are connected to each other through contact holes. More specifically, an interlayer insulating film is laminated on the semiconductor film. The contact hole is formed in the interlayer insulating film above the source region to pass through the interlayer insulating film. The data line is laminated on the interlayer insulating film while burying the contact hole. The source region of the semiconductor film is electrically connected to the data line through the contact hole.
The contact hole for electrically connecting the source region of the semiconductor film to the data line is generally formed in each of the plurality of pixel electrodes and the plurality of TFTs. For example, JP-A-10-177193 discloses a technique in which semiconductor films of adjacent TFTs are connected to each other by a common source region, that is, one source region is shared by adjacent TFTs. In this case, the shared source region of the semiconductor film and a data line are connected to each other by a common contact hole, that is, one contact hole.
In the technique disclosed in JP-A-10-177190, the common contact hole is formed above two adjacent edges of scanning lines formed for every pair of adjacent pixel electrodes.
More specifically, scanning lines are formed on a substrate formed of, for example, quartz, and the scanning line is patterned for every pixel. A first interlayer insulating film is formed on the scanning lines, and a semiconductor film is laminated on the first interlayer insulating film. Then, source regions are formed in parts of the semiconductor film positioned above spaces between the edges of the scanning lines, for examples by implanting a dopant.
At this time, the parts of the first Interlayer insulating film and the source regions positioned above the spaces between the edges of the scanning lines have the same shape as that between the edges of the scanning lines. Therefore, the first interlayer insulating film and the source region each have two edges. As a result, weak inclined surfaces are formed in the vicinities of the two edges of each of the first interlayer insulating film and the source region.
Then, a second interlayer insulating film is formed on the semiconductor film. Parts of the second interlayer insulating film positioned above the spaces between the edges of the scanning lines also have a shape corresponding to the shape between the edges of the scanning lines. Finally, contact holes are formed In the parts of the second interlayer insulating film positioned above the spaces between the edges of the scanning lines, that is, on the edges of the source regions to pass through the second interlayer insulating film.
Since the contact holes are formed on the spaces between the edges of the source regions, the weak inclined surfaces in the vicinities of the edges of the source regions can be damaged after the contact holes are formed.
As a result, the electrical connection between the source regions and the data lines are broken after the data lines are formed on the second interlayer insulating film, which causes image signals transmitted through the data lines not to be supplied to the pixel electrodes.